The present invention relates to a molded wood composite article, containing one or more molded depressions, and a method of making the molded wood composite article, having an inclined profile embossed or molded into a depression-interior portion of the article. More particularly, the molded wood composite article of the present invention is made from a combination of cellulosic material, such as cellulosic fibers or cellulosic particles, and a natural or synthetic binder, such as a phenol formaldehyde or urea formaldehyde resin, including at least about 80% cellulosic material, and molded from a mat having at least an upper surface formed from refined, fibrillated cellulosic fibers, e.g., a fiberboard mat, such as hardboard; or made from cellulosic particles, such as particle board. The major surfaces of the articles are molded from a planar layer of cellulosic material, e.g., a fiberboard mat, made either by the wet process or the dry process, preferably the dry process; or made from a layer of cellulosic particles and a resin binder. The planar layer of cellulosic material is molded when the cellulosic layer contains less than about 10% moisture, based on the dry weight of the cellulosic layer, regardless of the method of making the cellulosic layer. Essentially no gas venting is required until the molding operation is complete and the mold is opened. The depression-interior inclined molded profile does not blister, has relatively constant paint holdout, and provides better nesting, one article on another, whereby adjacent articles contact only on horizontal surfaces at distal ends of the depression-interior inclined molded profile, and not on the inclined profile, for shipping and storage without damage.
Man-made boards, such as fiberboard, e.g., hardboard; chipboard; oriented strand board-fiberboard composites; particle board; oriented strand board-particle board composites; and the like, commonly are embossed on their intended visible major surface in the manufacture of interior panelling, exterior siding, and particularly in the manufacture of door skins that are laminated to a support structure or frame, on both major surfaces, for replicating multi-panel doors having surfaces that are man made, rather than the very expensive natural wood xe2x80x9c6-panelxe2x80x9d doors. Commonly, such articles are molded from a planar cellulosic mat to include one or more interior or xe2x80x9cclosedxe2x80x9d depressions, within an interior of the article, such as one or more square or rectangular depressions that do not extend to an outer edge of the article.
The cellulosic fibers or particles used to form the loose mat, e.g., a two inch thick layer of cellulosic fibers, initially may be bone dry after the fibers have been dried and felted, but the cellulosic materials in such mats absorb moisture from the atmosphere and generally include about 2% to about 10% moisture when molded via hot pressing, depending upon the humidity in the region where such mats are stored and/or manufactured. A molded or embossed design in a layer of cellulosic material that leaves interior depressions in the molded article is difficult to provide without surface defects because gases formed during hot-pressing, e.g., vaporized moisture, cannot escape from the mold cavity via venting to an exterior edge of the molded article when the molded article is hot-pressed to a constant mold level completely surrounding the formed interior depressions.
In some mold designs formed in wood composites, venting is accomplished by disposing a gas pervious material, e.g., a temperature-resistant, gas-pervious fabric, between a back half of the mold cavity and a non-visible side of the product being molded, to achieve controlled gas venting without blister formation in the molded article. Controlled gas venting during the hot-press molding of wood composite articles, however, tends to disrupt the complete consolidation and bonding of the molded articles along the molded edges, due to the escape of gas at the edges, causing excessive scrap or wasted material. Wasted material results from trimming the incompletely consolidated edges, containing valuable cellulosic material and binder, which must be trimmed away to achieve solid, completely consolidated, scratch resistant man-made board material over the entire major, exterior surface of the trimmed molded article. Accordingly, when such waste cannot be tolerated, a mechanical dam is included, surrounding the mold cavity, to eliminate essentially all gas venting during the hot-press molding step to avoid xe2x80x9cpunkyxe2x80x9d edges that end up as waste.
A typical mechanical mold dam is a metal border extending from, and perpendicular to, one half of the mold or die, and extending, for example, 0.030 inch vertically toward the other half of the mold or die, to create sufficient pressure on the material being molded, completely surrounding the mold cavity, to prevent essentially all gas escape until the mold cavity is opened. Gas venting, when such mechanical dams are used, occurs almost exclusively as a result of opening the mold cavity upon completion of the hot-press molding step. The sudden reduction in pressure upon mold cavity opening, however, sometimes causes a sudden release of water vapor trapped beneath the upper surface of the molded article, thereby causing a portion of the visible molded surface to bubble or blisterxe2x80x94a portion of the molded surface delaminates from the remaining thickness because of the sudden escape of gas from an interior portion of the molded article. This blistering problem is most severe when attempting to mold detailed designs onto an inclined interior surface portion of closed depressions molded into wood composites.
Other problems occur in attempting to form the above-described inclined molded portions on an interior surface of closed depressions in a molded wood composite article, particularly when it is commercially necessary to paint such inclined surfaces to provide an aesthetically pleasing outer surface. One type of product, in particular, that must include excellent embossing detail and superior aesthetic qualities to be commercially acceptable, is a door skin that simulates a multi-panel natural wood door on both major faces of a support substrate or frame member. Door skins, or door faces, require detailed, inclined interior molded walls having a plurality of relatively close contours that include varied curves and planar surfaces. It has been found that these interior, inclined molded surfaces of interior inclined molded depression walls are very difficult to paint uniformly due to density differences, because of various curved and planar adjacent contours and due to the confined locations of the inclined surfaces within the relatively small, molded depressions. These angled or inclined surfaces on wall portions molded into depressions formed in the interior of the product are extremely difficult to provide with embossed surfaces representing, for example, a wood grain pattern, since such embossed texture on depression-interior inclined walls have a tendency to cause the article to stick to the mold cavity at the embossed inclined wall, causing fiber to pull away from the surface of the molded article when it is removed from the mold cavity.
Another problem common to the molded wood composite articles described above is in stacking a plurality of the molded articles for efficient shipping. Door skins, for example, when stacked one above another, having a xe2x80x9cbed and covexe2x80x9d depression profile, have a tendency to damage, particularly in the upper decorative surface of the lowermost articles, due to abrasive contact on the detailed depression-interior inclined surfaces, particularly on the convex, uppermost xe2x80x9cbeadxe2x80x9d of a xe2x80x9cbead and covexe2x80x9d Colonist(copyright) design, where aesthetics are most important, and where damage is most apparent.
The molded wood composite articles of the present invention solve some or all of the above-mentioned deficiencies in prior art molded wood composite articles to provide a molded wood composite article that has inclined, decorative depression-interior molded walls having upper, decorative inclined surfaces of relatively uniform density; can be painted with uniform paint hold-out; has molded, inclined surfaces that are accessible for buffability, in the preferred embodiment; and wherein the molded, inclined depression-interior surfaces are capable of being embossed with excellent texture or grain detail to provide an extremely aesthetic, detailed texture or grain design.
One patent, assigned to the Assignee of this application, Lynch, et al. U.S. Pat. No. 5,543,234, solves the above-mentioned deficiencies in the molded, inclined depression-interior surfaces, but the inclined surfaces are molded such that when stacked, one article above another, the inclined surfaces, at the ovolo or rounded areas, are in contact with the ovolo areas in an undersurface of an adjacent article. It has been found that such contact of stacked articles at rounded areas does not cause product damage so long as the mold core and mold cavity used to form the articles are exactly aligned during the formation of each article. However, if the mold core and mold cavity are not exactly aligned during product manufacture, the stacked articles are skewed from vertical, causing excessive loads on product ovolo areas, with subsequent cracking and scuffing at ovolo surfaces, where greatest aesthetics are required. The inclined, depression-interior walls of the articles of the present invention include a profile in the depression-interior, inclined molded surfaces such as an embossed xe2x80x9cbead and covexe2x80x9d design, that permits excellent stacking of the articles for efficient, and essentially damage-free shipping and storage, without any contact at the ovolo or rounded areas, while stacking more articles, one upon another, even if the mold core and mold cavity are misaligned during product formation. Damage-free stacking is achieved by providing a profile such that adjacent stacked articles are in contact only at horizontal, distal ends of the inclined molded surfaces, but adjacent, stacked, inclined and rounded molded surfaces do not make contact with each other during shipping, and are spaced at least 0.004 inch over the entire inclined wall span.
In brief, the present invention is directed to a molded wood composite article man-made from wood fibers or wood particles on at least an upper, molded surface of the article, and a method of manufacturing the article to include a relatively uniform density, detailed design contours and textured aesthetics on one or more molded depression-interior inclined surfaces, while preventing embrittlement, softness and blistering of the article along the depression-interior inclined surfaces. These attributes are achieved by molding one or more depressions into an initially planar layer of cellulosic material, wherein the molded depressions have one or more inclined walls that have upper surfaces, along essentially an entire inclined span, that include detailed design contours, including adjacent curved and planar portions, e.g., bead and cove. The inclined depression-interior molded walls, having upper surfaces that include the adjacent curved and planar contours, have a thickness or caliper measurement, measured normal to a tangent at any point along the upper (finished) contoured surface, that is smaller than the caliper so measured at horizontal, distal ends that are integral with the depression-interior contoured, inclined surface span, to make sure that the inclined surfaces of adjacent, stacked articles do not contact each other during shipping.
It has been found that the thickness or caliper along the entire span of contoured inclined depression-interior molded walls of a wood composite article, molded in accordance with the present invention, should be molded to be about 2% to about 15% thinner, preferably about 3% to about 10% thinner, and more preferably about 5% to about 8% thinner, than a thickness of adjoining horizontal portions at distal ends of the inclined walls of the wood composite articles.
It is apparent to those skilled in the art that the articles described herein can be formed from materials other than cellulosic materials, e.g., polymeric or plastic articles, while advantageously including one or more interior, inclined walls having a thickness that is smaller over the entire span of the inclined walls than the adjoining, integral, horizontal portions at the distal ends of the inclined, depression-interior molded walls of the article. Such an article, regardless of the material used to form the article, will nest, one article above another, without contact against the inclined, interior molded walls of the stacked articles for storage and transport without any surface scratching or other surface damage.
Accordingly, one aspect of the present invention is to provide a molded, wood composite article, and method of manufacturing the article, that includes interior molded depressions having an inclined, decorative surface that has a relatively uniform density along the entire inclined surface, which is not brittle or blistered as a result of the molding process, and such that the articles can be stacked, one upon another, without contacting adjacent articles at the inclined, depression-interior walls.
Another aspect of the present invention is to provide a molded, wood composite article, and method of manufacturing the article, containing at least about 80% cellulosic material, that is molded from an incompletely consolidated planar mat or preform using heat and pressure to include a decorative inclined surface in a molded depression within the interior of the article, wherein the inclined surfaces do not contact each other when a plurality of articles are stacked, one above another.
Still another aspect of the present invention is to provide a molded man-made wood composite article that includes a molded depression that includes adjacent curved and planar surfaces, e.g., xe2x80x9cbead and covexe2x80x9d on a depression-internal inclined surface, preferably having an inclination of about 10xc2x0 to about 40xc2x0, preferably about 15xc2x0 to about 30xc2x0 from a horizontal lower surface integral with a lower end of the inclined wall, that nests with a molded inclined wall undersurface of an identical wood composite article, without contact at the inclined walls, for storage and shipping without damage to the inclined surfaces; and wherein the inclined surfaces have a uniform paint-holdout capability and are easily embossed with a texture or other decorative design, e.g., simulating wood grain.
Another aspect of the present invention is to provide a decorative article of manufacture, that may be formed from plastic, or other non-wood material, that includes a depression having an interior inclined wall that will not contact an undersurface of an interior, inclined wall of an identical article stacked above to prevent damage of the inclined walls of the stacked, molded articles during shipping.
Still another aspect of the present invention is to provide a molded, man-made wood composite article, and method of making the article, that includes one or more interior molded depressions, wherein the depression has a length to depth ratio in the range of about 5.0 to about 8.5, preferably about 5.2 to about 8.2, more preferably about 5.2 to about 7.2, most preferably about 5.2 to about 6.2.
The above and other aspects and advantages of the articles and methods of the present invention will become more apparent from the following detailed description of the preferred embodiments, taken in conjunction with the drawings.